A microenvironment,rather than chemical,initiates the cardiomyogenic differentiation of marrow stromal cells

To investigate the potential of cardiomyogenic differentiation of rat bone marrow stromal cells (MSCs), they were exposed to 5-azacytidine tretments (single/repeat) at varying concentrations (3, 5, 10 μmol/L) and the fates of the cells were analyzed by immunocytochemistry, Western blot and the reporter gene of enhanced cyan fluorescent protein (ECFP) under the control of ventricular myosin light chain 2 (MLC2v) promoter. MSCs were also cocultured with cardiomyocytes for periods up to 16 days, the expression of cardiac myosin heavy chain (MHC) and troponin I (Tn I) proteins was analyzed. After the induction with 5-azacytidine, neither spontaneously beating cells nor myotubes were found; MHC and Tn I proteins were also undetectable and no ECFP-positive MSCs were detected. But when cocultured with cardiomyocytes, spontaneously contracting MSCs were observed and cardiac specific proteins could be detected. The results proved that the novel effects of 5-azacytidine on the cardiomyogenic differentiation of MSCs should be questioned and a direct intercellular communication with cardiomyocytes is necessary for MSCs to differentiate into cardiomyocytes. Foundation item: Supported by the Natural Science Foundation of Hubei Province (2002AB00150) Biography: LIU Wei-xin (1976-), male, Ph. D candidate, research direction: stem cell and cellular biology.